Terry Banthorpe, a neighbour, said the man who died had been threatening his own mother with a knife.

He said: “We had our door open and heard the quiet, muffled voice of an old lady saying that her son was trying to kill her.

“I’ve taken my dog outside the front at which point I’ve seen her son sort of like approaching me with a large knife, he’s seen the dog and decided to back off and go back into the house which is when I’ve decided to call the police.”

When officers arrived at the house at about 1900 GMT on Saturday they were confronted by the armed man, police said.

He was then shot with the police Taser gun.

“The man went into the house where he inflicted a more serious injury on himself,” said Bedfordshire Police.

“When officers found him, he was in urgent need of medical attention.”

Metal barbs

He was taken to Bedford South Hospital, where he was pronounced dead.

A Bedfordshire Police spokeswoman said on Sunday: “The deceased will not be named until an inquest is opened later this week.

“There will be no more statements about this incident until tomorrow when it will be decided whether this is an IPCC led investigation, or if it is referred back to Bedfordshire Police.”

When Tasers are fired, two metal barbs connected to the weapon by a thin wire pierce the skin before 50,00-volt electric charge is delivered.

Amnesty International claim more than 250 people have died in North America after being shot with a Taser.

But according to UK police, there have been “no severe or adverse reactions” since Taser was introduced by forces in 2003.